I would use synchronize for this task. Let's start with some table data.
datePart = repmat("02-01-20", 10, 1);
T = table(datePart, timePart, v.^2)
Convert the datePart and timePart variables in T into a datetime array and build a timetable using that array and the numeric data from T. You could use table2timetable to create TT1 but then you'd need to adjust the synchronize call to only interpolate on the numeric variables in TT1.
dateAndTime = datetime(T.datePart + " " + T.timePart, 'InputFormat', 'MM-dd-yy hh:mm');
TT1 = timetable(T.Var3, 'RowTimes', dateAndTime)
Make a second timetable with only part of the data. In reality the RowTimes of the two timetable arrays probably wouldn't be so nicely aligned, but it's good enough for purposes of this example.
TT2 = timetable(dateAndTime(1:2:end), v(1:2:end).^3)
Now synchronize the two timetable arrays. The RowTimes of the result should be the union of the RowTimes of TT1 and TT2, and we should fill in gaps using linear interpolation.
TT3 = synchronize(TT1, TT2, 'union', 'linear')
The elements in odd numbered rows (1st, 3rd, etc.) of Var1_TT2 in TT3 come directly from TT2. The elements in even numbered rows (2nd, 4th, etc.) are the result of linearly interpolating those values from TT2.Var1.